Core-level magnetic circular dichroism as a probe for electron-correlation effects

Abstract

Abstract We show how the spectral structure of the magnetic circular dichroism (MCD) in core-level spectroscopy can be analysed using angular momentum algebra. The results are supported by full-multiplet calculations in intermediate coupling, which for localized materials are in very good agreement with the experimental results. To demonstrate the general applicability we analyse a wide variety of systems. For didactical reasons we start off with the photoemission from an l shell and the spin–orbit split core j levels using a one-particle model, followed by the more realistic examples of rare earths 4f photoemission from an incompletely filled shell and N 4,5 X-ray absorption as the intermediate state in resonant photoemission. This gives a clear indication of the restrictions imposed by the one-particle model. We show that even for itinerant metals, such as nickel and iron, the 2p photoemission spectra cannot be explained using a one-particle model. Recent experimental results for the Ni 2p photoemission of nickel metal show that inter-configurational mixing has to be taken into account in order to understand the detailed structure of the MCD. Apart from its invaluable use to quantify the ground-state spin and orbital magnetic moments, MCD therefore also provides a powerful tool to study—in an element-specific way—the electron-correlation effects arising in a large variety of materials.